Hazards Associated with STCs

DOE-HDBK-1184-2004

2.5 Hazards Associated with STCs

2.5.1

Ingestion of Tritiated Particulates

Following ingestion, STCs lose some fraction of their tritium as HTO or soluble OBT

in digestive fluids. The fraction of the infused tritium lost via this mechanism varies

depending on the stability of the specific material in the gastrointestinal (GI) tract;

some particles lose essentially all of the tritium and others lose very little. In any

case, the only significant dose following ingestion of tritiated particles is due to the

resulting HTO or soluble OBT that is released. The remaining intact particles will

undergo fairly rapid elimination from the body, resulting in negligible internal doses.

Since HTO or soluble OBT is rapidly assimilated physiologically, this dose

component is readily assessed via urine bioassay.

2.5.2

Inhalation of Tritiated Particles

Following inhalation, tritiated particles may be deposited in the lung. Once

deposited in the lung, the infused tritium is removed from the body via two

mechanisms:

1. Dissolution of tritium from the particulate and absorption into the body as HTO

or soluble OBT, and removal through urine, expired air, and perspiration.

2. Mechanical transport of the particulate itself to the GI tract and removal through

feces. (Inhaled tritiated particles removed to the GI tract will cause dose in the

same manner as ingested triatiated particles, as described above.)

Removal of ITPs from the lung through mechanical transport can be slow. ITPs

can, therefore, reside in the lung for a considerable amount of time. Accordingly, a

significant portion of the entire committed effective dose equivalent resulting from

the decay of the associated tritium atoms results from deposition in the lungs. The

lung receives 85% of the committed effective dose equivalent (CEDE) from Type M

ITPs and 96% of the CEDE from Type S ITPs (ICRP 71).

2.5.3

Skin absorption of OBT

Solvent OBT

Solvent OBT can, if spilled as liquid on the skin, produce a skin absorption pathway.

The potential hazard of this pathway should be assessed using known or analyzed

activity of the liquid. Solvent OBT absorbed through the skin can be assessed

using urine bioassay.

OBT Oils

Tritiated oils can be found in pumps and compressors located in areas where work

with tritium has been conducted. Trivedi (1995), in experiments on rats, has shown

that tritiated oils can be absorbed by mammalian skin. Accordingly, skin absorption

is a valid intake pathway for oil components. See section 4.4.3 for additional

information on skin absorption of OBTs.